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Horm Metab Res 2002; 34(2): 93-101
DOI: 10.1055/s-2002-20522
Original Clinical

© Georg Thieme Verlag Stuttgart · New York

Substrate Turnover and Oxidation During Moderate-Intensity Exercise Following Acute Plasma Volume Expansion

B.  D.  Roy 1 , H.  J.  Green 1 , S.  M.  Grant 1 , M.  A.  Tarnopolsky 2
  • 1 Department of Kinesiology, University of Waterloo, Waterloo, Canada
  • 2 Department of Medicine/Kinesiology, McMaster University, Hamilton, Canada
Further Information

Publication History

5 January 2001

21 August 2001

Publication Date:
04 March 2002 (online)

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Abstract

In previous work using prolonged, light cycle exercise, we were unable to demonstrate an effect of acute plasma volume (PV) expansion on glucose kinetics or substrate oxidation, despite a decline in whole-body lipolysis (Phillips et al., 1997). However, PV is known to decrease arterial O2 content. The purpose of this study was to examine whether substrate turnover and oxidation would be altered with heavier exercise where the challenge to O2 delivery is increased. Eight untrained males (VO2max = 3.52 ± 0.12 l/min) twice performed 90 min of cycle ergometry at 62 % VO2peak, both prior to (CON) and following induced plasma volume expansion (Dextran [6 %] or Pentaspan [10 %]) (6.7 ml/kg) (PVX). Glucose and glycerol kinetics were determined with primed constant infusions of [6.6-2H2] glucose and [2H5] glycerol, respectively. PVX resulted in a 15.8 ± 2.2 % increase (p < 0.05) in PV. Glucose and glycerol appearance (Ra) and utilization (Rd), although increasing progressively (p < 0.05) with exercise, were not different between conditions. Similarly, no differences in substrate oxidation, either fat or carbohydrate, were observed between the two conditions. Prolonged exercise resulted in an increase (p < 0.05) in plasma glucagon and a decrease (p < 0.05) in plasma insulin during both conditions. With PVX, the exercise-induced increase in glucagon was diminished (p < 0.05). We conclude that impairment in O2 content mediated by an elevated PV does not alter glucose, and glycerol kinetics or substrate oxidation even at moderate exercise intensity.

Key words

Glucose Turnover - Glycerol Turnover - Lipolysis - Stable Isotopes - Exercise - Hypervolemia

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Dr. H. J. Green

Department of Kinesiology · University of Waterloo

Waterloo, ON, N2L3G1 · Canada

Phone: + 1 (519) 888-4567, x3454

Fax: + 1 (519) 885-0470

Email: green@healthy.uwaterloo.ca

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